The invention relates to a reloadable ribbon cassette for a typewriter or office machine of similar construction of the type having an opening closable by a cover in the top of a cassette housing for the exchange of a supply spool for unwinding and a take-up spool for winding up a ribbon, with the supply and take-up spools being controllable by means of a plurality of movable drive parts arranged in an operative configuration for guiding and transporting said ribbon including a braking device for blocking and releasing said supply spool and a feed roller, the take-up spool being driven by means of said feed roller equipped with a sprocket wheel which can be brought into engagement with the ribbon by means of a spring.
U.S. Pat. No. 3,731,781 discloses a removable cassette for a carbon ribbon to be used in a printer having a rotatable drive element for ribbon advance, with the cassette being composed of a housing accommodating a ribbon supply spool and a take-up spool. A pivotal feed roller equipped with a sprocket wheel here cooperates with a take-up spool disposed on a stationary axis to wind up the carbon ribbon. For exchanging the cassette, the feed roller and the sprocket wheel must first be put out of engagement with the take-up spool. This exchange process requires a plurality of manipulations since, after insertion of the new cassette in the receiving device of the machine, the feed roller must also be brought back into engagement with the take-up spool.
German Patent No. 2,553,329 discloses a ribbon cassette for a typewriter or office machine of a similar construction in which the feed roller and its sprocket wheel are disposed in the cassette. The feed roller here remains in constant engagement with the carbon ribbon on the take-up spool. In this way it is possible to perform the exchange of ribbon cassettes with only one hand. This prior art ribbon cassette is very expensive since the members for driving the carbon ribbon contained in the ribbon cassette ar discarded together with the ribbon when it is used up. Since, moreover, the feed roller is always in engagement with the take-up spool and the drive elements are mounted, on the one hand, in the bottom portion and, on the other hand, in the cover which is fixed to the bottom portion, it is not possible to exchange the supply and take-up spools.
The above-mentioned drawbacks are overcome by DE-OS 3,524,730.4 in that the ribbon cassette is provided with a cover which closes an opening and that a supply spool for unwinding and a take-up spool for winding up the ribbon are freely placeable onto and rotatable on bearing pins in the cassette. The free end of the ribbon from the full supply spool is here provided with a fastening means serving to thread the ribbon around guide points in the cassette and being fixable to the core of the take-up spool in order to wind up the ribbon. With this cassette, the operator performing the exchange of spools still must have a certain amount of skill to properly thread the ribbon without permitting drive and guide elements disposed in the cassette to fall out of the cassette.